Human herpesvirus 8: Is it a tumor virus?

Human herpesvirus 8 (HHV-8), also termed Kaposi's sarcoma-associated herpes virus, was identified in Kaposi's sarcoma (KS) biopsy specimens in 1994. Th e epidemiological data available to date indicate a strong association of H HV-8 with KS. It appears that HHV-8 is necessary for KS development. HHV-8 DNA is invariably found in all epidemiological forms of KS and primary effu sion lymphomas. In contrast, HHV-8 DNA is rarely found in various tumor and nontumor tissues from patient groups not at risk of KS. Although current s erology does not allow us to assess the HHV-8 prevalence in the general pop ulation, high titers of HHV-8 antibodies are almost exclusively found in KS risk groups. In addition, HHV-8 seroconversion has been shown to precede K S development. The mechanisms and genes involved in HHV-8 pathogenesis are less clear. HHV-8 belongs to a family of transforming viruses, and several candidate oncogenes have been identified by using rodent fibroblast transfo rmation assays. However, expression of most of these genes could not be sho wn in latently infected tumor cells. As the HHV-8 genome encodes several cy tokines and cytokine receptor homologues, HHV-8 may also promote KS pathoge nesis through paraendocrine mechanisms.